Pin sliding disc brake

ABSTRACT

The present specification provides a caliper for use in a disc brake. The caliper has at least two body sections which are clamped together by one or more bolts, each bolt having a bore extending axially therethrough, the bores acting as pin guides for the pins secured to the torque taking member, in the complete brake. Thus only a pair of holes are required to be formed in the caliper body sections, improving the strength and rigidity of the caliper and keeping manufacturing costs to a minimum.

DESCRIPTION

The present invention relates to the construction of a pin slidingcaliper for use in a disc brake.

With the tendency towards weight reduction, brake construction issometimes of composite form, utilising in certain cases a combination ofalloy to give weight reduction in caliper sections which are not loadbearing, and cast irons etc., to give strength and durability where itis so required. A typical construction may, for example, have an alloypiston housing bolted to an S.G. iron bridge, the two parts forming thecaliper member, the caliper member being slidably engaged with a castiron torque-taking member. In an alternative construction the calipermember may have the piston housing and the bridge integrallymanufactured from light weight alloy. A disadvantage with the compositehousing and bridge construction is that at least two, and in some casesfour bolts are required to clamp the two parts together. Also, in theaforementioned constructions of caliper member, when an automaticadjuster/parking brake facility is fitted, the caliper member may havean additional cover plate bolted to the rear of the piston housing, suchthat the components making up the adjuster etc., can be assembledthereupon. Thus the number of components making up the bridge, thepiston housing, the cover plate and the bolts holding the componentstogether, becomes inordinately large. Also, as bores have to be drilledand tapped for the said bolts, it will be appreciated that the cost ofthe brake becomes correspondingly more expensive to manufacture.

A further disadvantage that may occur when a caliper construction iswholly alloy, and in particular when the alloy provides a direct guidefor the steel pin sliding connection between caliper member and torquetaking member, lies in the fact that the pin guide bores may be moresusceptible to wear than for example, when the steel pins are guided incast iron bores.

The aim of the present invention is to provide a caliper constructionwhich is not so susceptible to wear, is less expensive to manufacture,and has additional advantages over prior art constructions of a similartype.

According to the present invention there is provided a caliper for usein a disc brake, comprising at least two caliper body sections clampedtogether by means of a bolt which has a bore extending axiallytherethrough, said bore serving as a guide for a pin in the completedisc brake.

In a preferred embodiment of the present invention both the cylinderhousing and an adjuster/parking brake housing, are made of light weightmetal alloy and are clamped together by two hollow bolts which engagewith clearance through bores in the adjuster/parking brake housing andare screw threaded into bores in the cylinder housing. These hollowbolts act as guides for axially slidable pins secured to a torque takingmember of the disc brake.

Thus, the provision of the hollow bolts both reduces the number of holesrequired to be produced, reducing costs, and provides a steel sleeve asa pin guide, increasing guide life as compared to an alloy guide. Thepresent invention thereby enables a composite caliper construction tohave the lighter weight advantage but not the previously inherentdisadvantage.

Further the present invention has a number of additional advantages. Oneis that the hollow bolts are of such a diameter as to convenientlyprovide a large thread shear area in the alloy; this being a requirementfor all alloys. Another lies in the fact that a groove to retain aconvoluted boot for sealing the sliding pin against extraneous matterand weathering, can be formed in the end of the or each hollow boltobviating the previous requirement for an undercut or counterbore forthis purpose.

Also, the present invention provides for easier assembly, adjustment andtesting of an automatic adjuster/parking brake mechanism as referred toin the preferred embodiment, and different adjuster housings can besimply fitted to a universal piston housing to suit particular customerrequirements e.g. in respect of hydraulic porting and parking brakelever position.

The present invention will now be further described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a partially cutaway sectional plan view of a preferredembodiment of the present invention installed in a disc brake; and

FIG. 2 is an end elevation of the disc brake illustrated in FIG. 1.

The caliper member shown in the accompanying drawings and generallydesignated 1, comprises a piston housing 3 and an adjuster/parking brakehousing 5 which contains an adjuster mechanism 7 (not detailed), theadjuster mechanism 7 being operable by cam 9 and strut 11.

Housings 3 and 5 are clamped together by hollow bolts 13 which arecircumferentially spaced apart from each other with respect to the disc(not shown) of the complete brake. Hollow bolts 13 each have a threadedportion 15 and a flanged head portion 17 in the open end of which aprotective plug 19 is located. Each bolt 13 engages through a bore 21 inthe adjuster/parking brake housing and is screwed into a threaded bore23 in the piston housing 3, the adjuster/parking brake housing beingclamped between the piston housing 3 and the head portion 17 of eachbolt 13.

In use, as can be seen in the cross-sectional part of FIG. 1, a pin 25engages in the bore 14 in each hollow bolt 13 and is axially slidabletherein, each pin 25 being secured to the torque taking member 27 of thebrake. Whilst the pin 25 is shown in FIG. 1 as a two-part constructioncomprising pin bolt 29 and shaft 31, clearly the pin can alternativelybe of integral construction and be simply screwed into a complementarilythreaded bore in the torque taking member.

Thus by virtue of the present invention, in the embodiment illustrated,both the adjuster/parking brake housing 5 and the piston housing 3 andintegral bridge 33, can be made of a suitable light weight alloy, hollowbolts 13 providing durable guides for the sliding pin 25. Thisconstruction provides for a light weight caliper member. Further, asbolts 13 act both as pin guides and also clamp the housings 3 and 5together, the number of bores required to be drilled in the caliper isreduced as compared to prior constructions, enhancing the strength ofthe caliper member and reducing manufacturing costs.

The simple construction of the caliper of the present invention alsoprovides for easier assembly, adjustment and testing of the automaticadjuster/parking brake mechanism and allows for a universal pistonhousing 3 to be used in many installations whilst the adjuster housing 5can be varied to suit any particular customer requirement e.g.particular hydraulic porting and parking brake lever arrangement.

The illustrated construction (FIG. 1) provides an annular groove 35 inthe end of each hollow bolt 13, which groove 35 receives and retains thesealing boot 37 which protects the sliding surface of pin 25. Thisobviates the necessity for undercutting or providing the caliper housing3, 5 with a counterbore as previously required for retaining the slidingpin sealing boot. Thus manufacturing costs are again reduced.

Also, although this construction is particularly advantageous in an allalloy construction of caliper member, where good pin to bore wearcharacteristics are preferred, it is equally suited to a constructionof, for example a cast iron piston housing in combination with an alloyparking brake housing, with the same advantages.

The present invention thus provides a lightweight caliper for a pinsliding disc brake wherein the construction is simplified andmanufacturing costs reduced whilst durability and hence life, ismaintained.

I claim:
 1. A pin sliding disc brake comprising a caliper and a torquetaking member, a sliding pin connection interconnecting said caliper andtorque taking member and including a pin connected to the torque takingmember, said caliper comprising at least two caliper body sections, abolt clamping said body sections together and having a bore extendingaxially therethrough, said bore receiving said pin connected to thetorque taking member and serving as a guide for said pin whereby saidbolt serves both as a caliper clamp and also as a pin guide.
 2. A discbrake according to claim 1, wherein said at least two caliper bodysections are also clamped together by means of a second bolt spacedapart from said first mentioned bolt, said second bolt also having abore extending axially therethrough.
 3. A disc brake according to claim1 or claim 2, wherein each bolt has a flanged head portion and athreaded portion.
 4. A disc brake according to claim 2, wherein at leastone of the caliper body sections is made of light weight metal alloy. 5.A disc brake according to claim 2, wherein a second pin is secured tosaid torque taking member and is received in the bore of said secondbolt, both of said bolts being axially slidable in said bores.
 6. A discbrake according to claim 1, wherein one body section of said calipercomprising a cylinder housing and the other section comprising anadjuster/parking brake housing.
 7. A disc brake according to claim 6,wherein said caliper body sections are clamped together by two hollowbolts which engage with clearance through bores in the adjuster/parkingbrake housing and are screw threaded into bores in the cylinder housing.8. A disc brake according to claim 1, wherein a removable plug closesoff one end of the bore in the bolt.
 9. A disc brake according to claim1, wherein the end region of the bolt, which receives said pin, has agroove for retaining a protective boot.